Nitrogenated aromatic heterocyclic derivative, and organic electroluminescent element using same

ABSTRACT

A nitrogen-containing aromatic heterocyclic derivative in which a nitrogen atom of an indenocarbazole skeleton optionally having a hetero atom or an indenoindole skeleton optionally having a hetero atom is bonded to a dibenzofuran or a dibenzothiophene directly or indirectly. The derivative realizes an organic EL device with a high emission efficiency and a long lifetime.

TECHNICAL FIELD

The present invention relates to nitrogen-containing aromaticheterocyclic derivatives and organic electroluminescence devices(hereinafter also referred to as organic EL device).

BACKGROUND ART

Organic electroluminescence (EL) devices are much expected to be usefulas inexpensive, large-sized full color display devices of solid stateemission type and many developments have been made thereon. An organicEL device is generally constructed from a light emitting layer and apair of opposite electrodes sandwiching the light emitting layer. Whenan electric field is applied between the electrodes, electrons areinjected from a cathode and holes are injected from an anode into thelight emitting layer. The injected electrons recombine with the injectedholes in the light emitting layer to form excited states. When theexcited states return to the ground state, the energy is released aslight.

A phosphorescent organic EL device wherein a phosphorescent organicmaterial is used in the light emitting layer has been proposed.Utilizing the singlet excited state and the triplet excited state of thephosphorescent organic material, a high emission efficiency can beobtained by the phosphorescent organic EL device. When electrons andholes are recombined in an organic EL device, singlet excitons andtriplet excitons may generate in a ratio of 1:3 in accordance with theirdifference in the spin multiplicity. Therefore, an organic EL deviceemploying the phosphorescent emitting material would achieve an emissionefficiency three to four times higher than that of an organic EL deviceemploying only the fluorescent emitting material.

The early organic EL device requires a high driving voltage and isinsufficient in the emission efficiency and durability. To eliminatethese problems, various technical improvements have been made.

The improved emission efficiency and the prolonged lifetime are veryimportant for reducing the power consumption of displays and improvingthe durability. Therefore, further improvements have been stillrequired. In addition, many studies have been made in order to improvethe emission efficiency and the device lifetime of organic EL devicesemploying a phosphorescent emitting material.

A carbazole derivative has been used particularly as a phosphorescenthost material because it has a high triplet energy. It has been alsostudied to use the carbazole derivative as a hole transporting materialin the vicinity of a phosphorescent host, because the carbazolederivative makes the ionization potential (Ip) shallow to increase thehole transporting ability.

The carbazole derivative has been modified in its molecular structure.Patent Document 1 discloses a derivative having an indenoindoleskeleton, Patent Document 2 discloses a derivative having anindenocarbazole skeleton, and Patent Document 3 discloses a derivativehaving an indolocarbazole skeleton.

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: JP 2010-40829A-   Patent Document 2: WO 2010/114267-   Patent Document 3: WO 2011/049063

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

However, the inventors have found that the transporting properties ofthe proposed carbazole derivatives are difficult to control because oftheir relatively high electron transporting ability, and therefore, therecombination zone is sifted toward the hole transporting layer side toadversely affect the efficiency and lifetime.

The present invention has been made to solve the above problem and itsobject is to provide an organic EL material for realizing a highlyefficient, long-lifetime organic EL device.

Means for Solving Problem

As a result of extensive research to achieve the above object, theinventors have found that the above problems are solved by anitrogen-containing aromatic heterocyclic derivative wherein a nitrogenatom of an indenoindole skeleton or an indenocarbazole skeleton eachoptionally having a hetero atom is bonded to a carbon atom constitutingthe benzene ring of a fluorene skeleton which may include a hetero atom.The present invention is based on this finding.

The present invention provides:

1. A nitrogen-containing aromatic heterocyclic derivative represented byformula (1-1) or (1-2):

wherein:

a ring A is represented by formula (1a) or (1b):

ring carbon atoms C₁ and C₂, C₃ and C₄, C₄ and C₅, or C₅ and C₆ areshared with an adjacent ring;

X represents NR₅, CR₆R₇, SiR₆R₇, an oxygen atom, or a sulfur atom;

each of W and Z independently represents a single bond, CR₆R₇, SiR₆R₇,an oxygen atom, or a sulfur atom;

L₁ represents a single bond, an arylene group having 6 to 30 ring carbonatoms, or a heteroarylene group having 5 to 30 ring atoms;

each of R₁ to R₇ independently represents a linear or branched alkylgroup having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15ring carbon atoms, a substituted or unsubstituted silyl group, an arylgroup having 6 to 30 ring carbon atoms, a heteroaryl group having 5 to30 ring atoms, a halogen atom, or a cyano group, or adjacent two groupsof R₁ to R₇ are bonded to each other to from a saturated or unsaturateddivalent group which completes a ring;

each of a, c and d independently represents an integer of 0 to 4;

b represents an integer of 0 to 3;

e represents an integer of 0 to 2; and

Q represents a structure represented by formula (1c):

wherein:

Y represents an oxygen atom or a sulfur atom;

L₂ represents a single bond, an arylene group having 6 to 30 ring carbonatoms, or a heteroarylene group having 5 to 30 ring atoms, provided thatwhen L₂ is bonded to a carbon atom at 2-position of the structurerepresented by formula (1c), L₂ represents an arylene group having 6 to30 ring carbon atoms or a heteroaryl group having 5 to 30 ring atoms;

each of R₈ and R₉ independently represents a linear or branched alkylgroup having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15ring carbon atoms, a substituted or unsubstituted silyl group, an arylgroup having 6 to 30 ring carbon atoms, a heteroaryl group having 5 to30 ring atoms, a halogen atom, or a cyano group, or adjacent two groupsof R₈ and R₉ are bonded to each other to from a saturated or unsaturateddivalent group which completes a ring;

f represents an integer of 0 to 3; and

g represents an integer of 0 to 4;

2. The nitrogen-containing aromatic heterocyclic derivative according toitem 1, wherein W of formulae (1-1) and (1-2) represents a single bondand Z of formulae (1a) and (1b) represents a single bond;

3. The nitrogen-containing aromatic heterocyclic derivative according toitem 2, which is represented by formula (2-1) or (2-2);

wherein R₁, R₃, R₄, a, d, e, X, and Q are as defined above;

4. The nitrogen-containing aromatic heterocyclic derivative according toitem 2, which is represented by formula (3-1) or (3-2);

wherein R₁, R₃, R₄, a, d, e, X, and Q are as defined above;

5. The nitrogen-containing aromatic heterocyclic derivative according toitem 2, which is represented by formula (4-1);

wherein R₁, R₃, R₄, a, d, e, X, and Q are as defined above;

6. The nitrogen-containing aromatic heterocyclic derivative according toitem 2, which is represented by formula (5-1) or (5-2):

wherein R₁, R₂, a, c, X, and Q are as defined above;

7. The nitrogen-containing aromatic heterocyclic derivative according toany one of items 1 to 6, wherein L₂ represents a single bond;

8. The nitrogen-containing aromatic heterocyclic derivative according toany one of items 1 to 6, wherein L₂ represents a structure representedby any one of formulae (7a) to (7c):

wherein:

each of R₁₁ to R₁₃ independently represents a linear or branched alkylgroup having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15ring carbon atoms, a substituted or unsubstituted silyl group, an arylgroup having 6 to 20 ring carbon atoms, a heteroaryl group having 5 to20 ring atoms, a halogen atom, or a cyano group, or adjacent two groupsof R₁₁ to R₁₃ are bonded to each other to from a saturated orunsaturated divalent group which completes a ring;

each of R₁₄ and R₁₅ independently represents a linear or branched alkylgroup having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15ring carbon atoms, an aryl group having 6 to 20 ring carbon atoms, or aheteroaryl group having 5 to 20 ring atoms; and

each of k1 to k3 independently represents an integer of 0 to 4;

9. The nitrogen-containing aromatic heterocyclic derivative according toany one of items 1 to 8, wherein X represents NR₅;

10. The nitrogen-containing aromatic heterocyclic derivative accordingto any one of items 1 to 8, wherein X represents an oxygen atom;

11. The nitrogen-containing aromatic heterocyclic derivative accordingto any one of items 1 to 8, wherein X represents a sulfur atom;

12. The nitrogen-containing aromatic heterocyclic derivative accordingto any one of items 1 to 8, wherein X represents CR₆R₇;

13. The nitrogen-containing aromatic heterocyclic derivative accordingto any one of items 1 to 8, wherein X represents SiR₆R₇;

14. The nitrogen-containing aromatic heterocyclic derivative accordingto any one of items 1 to 13, wherein Y represents an oxygen atom;

15. The nitrogen-containing aromatic heterocyclic derivative accordingto any one of items 1 to 13, wherein Y represents a sulfur atom;

16. The nitrogen-containing aromatic heterocyclic derivative accordingto any one of items 1 to 15, wherein L₂ is bonded to a carbon atom at4-position of the structure represented by formula (1c);

17. The nitrogen-containing aromatic heterocyclic derivative accordingto any one of items 1 to 16, which is for use as a material for organicelectroluminescence device;

18. The nitrogen-containing aromatic heterocyclic derivative accordingto any one of items 1 to 16, which is for use as a hole transportingmaterial for organic electroluminescence device;

19. An organic electroluminescence device comprising organic thin filmlayers between an anode and a cathode, wherein the organic thin filmlayers comprise a light emitting layer and at least one layer of theorganic thin film layers comprises the nitrogen-containing aromaticheterocyclic derivative according to any one of items 1 to 16;

20. The organic electroluminescence device according to item 19, whereinthe organic thin film layers comprise a hole transporting layer and thehole transporting layer comprises the nitrogen-containing aromaticheterocyclic derivative;

21. The organic electroluminescence device according to item 19 or 20,wherein the light emitting layer comprises a phosphorescent material;

22. The organic electroluminescence device according to item 21, whereinthe phosphorescent material is an ortho metallated complex of a metalselected from iridium (Ir), osmium (Os) and platinum (Pt); and

23. The organic electroluminescence device according to any one of items20 to 22, wherein the hole transporting layer is made in contact with alayer comprising a compound represented by formula (A):

wherein:

R²¹ to R²⁶ may be the same or different and each independently representa cyano group, —CONH₂, a carboxyl group, or —COOR²⁷, wherein R²⁷represents an alkyl group having 1 to 20 carbon atoms or a cycloalkylgroup having 3 to 20 carbon atoms; and

one or more of a pair of R²¹ and R²², a pair of R²³ and R²⁴, and a pairof R²⁵ and R²⁶ may be bonded to each other to form a group representedby —CO—O—CO—.

Effect of the Invention

According to the present invention, a long-lifetime organic EL devicewith a high emission efficiency and an organic EL material whichrealizes such a device are provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view of an exemplified organic ELdevice of the invention.

MODE FOR CARRYING OUT THE INVENTION

The carbon number of a to b in the expression of “a substituted orunsubstituted X group having a to b carbon atoms” is the carbon numberof the unsubstituted X group and does not include the carbon atom of theoptional substituent.

The definition of hydrogen atom includes isotopes different in theneutron numbers, i.e., light hydrogen (protium), heavy hydrogen(deuterium), and tritium.

Nitrogen-Containing Aromatic Heterocyclic Derivative

The nitrogen-containing aromatic heterocyclic derivative of theinvention is represented by formula (1-1) or (1-2):

In formula (1-1) or (1-2):

a ring A is represented by formula (1a) or (1b):

wherein ring carbon atoms C₁ and C₂, C₃ and C₄, C₄ and C₅, or C₅ and C₆are shared with an adjacent ring.

X represents NR₅, CR₆R₇, SiR₆R₇, an oxygen atom, or a sulfur atom.

Each of W and Z independently represents a single bond, CR₆R₇, SiR₆R₇,an oxygen atom, or a sulfur atom.

L₁ represents a single bond, an arylene group having 6 to 30, preferably6 to 18 ring carbon atoms, or a heteroarylene group having 5 to 30,preferably 5 to 18 ring atoms.

Each of R₁ to R₇ independently represents a linear or branched alkylgroup having 1 to 15, preferably 1 to 5 carbon atoms, a cycloalkyl grouphaving 3 to 15, preferably 5 to 12 ring carbon atoms, a substituted orunsubstituted silyl group, an aryl group having 6 to 30, preferably 6 to18 ring carbon atoms, a heteroaryl group having 5 to 30, preferably 5 to18 ring atoms, a halogen atom, or a cyano group, or adjacent two groupsof R₁ to R₇ are bonded to each other to from a saturated or unsaturateddivalent group which completes a ring.

Each of the subscript a, c and d independently represents an integer of0 to 4, preferably 0 to 2.

The subscript b represents an integer of 0 to 3, preferably 0 to 2.

The subscript e represents an integer of 0 to 2, preferably 0 or 1.

Q represents a structure represented by formula (1c):

In formula (1-c):

Y represents an oxygen atom or a sulfur atom.

L₂ represents a single bond, an arylene group having 6 to 30, preferably6 to 18 ring carbon atoms, or a heteroarylene group having 5 to 30,preferably 5 to 18 ring atoms, provided that when L₂ is bonded to acarbon atom at 2-position of the structure represented by formula (1c),L₂ represents an arylene group having 6 to 30, preferably 6 to 18 ringcarbon atoms or a heteroaryl group having 5 to 30, preferably 5 to 18ring atoms.

Each of R₈ and R₉ independently represents a linear or branched alkylgroup having 1 to 15, preferably 1 to 5 carbon atoms, a cycloalkyl grouphaving 3 to 15, preferably 5 to 12 ring carbon atoms, a substituted orunsubstituted silyl group, an aryl group having 6 to 30, preferably 6 to18 ring carbon atoms, a heteroaryl group having 5 to 30, preferably 5 to18 ring atoms, a halogen atom, or a cyano group, or adjacent two groupsof R₈ and R₉ are bonded to each other to from a saturated or unsaturateddivalent group which completes a ring.

The subscript f represents an integer of 0 to 3, preferably 0 to 2.

The subscript g represents an integer of 0 to 4, preferably 0 to 2.

Examples of the arylene group for L₁ and L₂ include divalent residues ofaromatic compounds selected from benzene, naphthalene, phenanthrene,biphenyl, terphenyl (inclusive of isomers), quaterphenyl (inclusive ofisomers), fluoranthene, triphenylene, 9,9-dimethylfluorene,benzo[c]phenanthrene, benzo[a]triphenylene, naphtho[1,2-c]phenanthrene,naphtho[1,2-a]triphenylene, dibenzo[a,c]triphenylene, andbenzo[b]fluoranthene, with a 1,4-phenylene group, a 1,3-phenylene group,a naphthalene-2,6-diyl group, a naphthalene-2,7-diyl group, and a9,9-dimethylfluorene-2,7-diyl group being preferred.

Examples of the alkyl group for R₁ to R₉ include a methyl group, anethyl group, a n-propyl group, an isopropyl group, a n-butyl group, as-butyl group, an isobutyl group, a t-butyl group, a n-pentyl group, an-hexyl group, a n-heptyl group, a n-octyl group, a n-nonyl group, an-decyl group, a n-undecyl group, a n-dodecyl group, a n-tridecyl group,a n-tetradecyl group, a n-pentadecyl group, a n-hexadecyl group, an-heptadecyl group, a n-octadecyl group, a neopentyl group, a1-methylpentyl group, a 2-methylpentyl group, a 1-pentylhexyl group, a1-butylpentyl group, a 1-heptyloctyl group, and a 3-methylpentyl group,with a methyl group, a t-butyl group, an ethyl group, a n-propyl group,and an isopropyl group being preferred.

Examples of the cycloalkyl group for R₁ to R₉ include a cyclopropylgroup, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, anda cyclooctyl group, with a cyclopentyl group and a cyclohexyl groupbeing preferred.

Examples of the substituted silyl group for R₁ to R₉ include —SiH₂R,—SiHR₂, and —SiR₃, wherein R is selected from the alkyl groups mentionedabove and two or three R groups may be the same or different, with atrimethylsilyl group, a triethylsilyl group, and a t-butyldimethylsilylgroup being preferred.

Examples of the aryl group for R₁ to R₉ include a phenyl group, anaphthyl group, a phenanthryl group, a biphenyl group, a terphenylgroup, a quaterphenyl group, a fluoranthenyl group, a triphenylenylgroup, a 9,9-dimethylfluorenyl group, a benzo[c]phenanthrenyl group, abenzo[a]triphenylenyl group, a naphtho[1,2-c]phenanthrenyl group, anaphtho[1,2-a]triphenylenyl group, a dibenzo[a,c]triphenylenyl group,and a benzo[b]fluoranthenyl group, with a phenyl group, a 4-biphenylgroup, a 3-biphenyl group, a 5′-m-terphenyl group, a 1-naphthyl group, a9,9-dimethylfluorene-2-yl group, a 2-naphthyl group, and a9-phenanthrenyl group being preferred.

The heteroaryl group for R₁ to R₉ preferably include at least one heteroatom selected from a nitrogen atom, an oxygen atom and a sulfur atom.Examples thereof include a pyrrolyl group, a furyl group, a thienylgroup, a pyridyl group, a pyridazinyl group, a pyrimidinyl group, apyrazinyl group, a triazinyl group, an imidazolyl group, an oxazolylgroup, a thiazolyl group, a pyrazolyl group, an isoxazolyl group, anisothiazolyl group, an oxadiazolyl group, a thiadiazolyl group, atriazolyl group, an indolyl group, an isoindolyl group, a benzofuranylgroup, an isobenzofuranyl group, a benzothiophenyl group, an indolizinylgroup, a quinolizinyl group, a quinolyl group, an isoquinolyl group, acinnolyl group, a phthalazinyl group, a quinazolinyl group, aquinoxalinyl group, a benzimidazolyl group, a benzoxazolyl group, abenzothiazolyl group, an indazolyl group, a benzisoxazolyl group, abenzisothiazolyl group, a carbazolyl group, a dibenzofuranyl group, adibenzothiophenyl group, a phenanthridinyl group, an acridinyl group, aphenanthrolinyl group, a phenazinyl group, a phenothiazinyl group, aphenoxazinyl group, and a xanthenyl group, with a furyl group, a thienylgroup, a benzofuranyl group, a benzothiophenyl group, a dibenzofuranylgroup, and a dibenzothiophenyl group being preferred.

Examples of the divalent group formed by the adjacent groups of R₁ to R₉which are boned to each other include a butane-1,4-diyl group and a1,3-butadiene-1,4-diyl group.

Each of W and Z preferably represents a single bond.

L₂ preferably represents a single bond or a structure represented by anyone of formulae (7a) to (7c):

wherein:

each of R₁₁ to R₁₃ independently represents a linear or branched alkylgroup having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15ring carbon atoms, a substituted or unsubstituted silyl group, an arylgroup having 6 to 20 ring carbon atoms, a heteroaryl group having 5 to20 ring atoms, a halogen atom, or a cyano group, or adjacent two groupsof R₁₁ to R₁₃ are bonded to each other to from a saturated orunsaturated divalent group which completes a ring;

each of R₁₄ and R₁₅ independently represents a linear or branched alkylgroup having 1 to 15 carbon atoms, a cycloalkyl group having 3 to 15ring carbon atoms, an aryl group having 6 to 20 ring carbon atoms, or aheteroaryl group having 5 to 20 ring atoms; and

each of k1 to k3 independently represents an integer of 0 to 4.

In formula (1c), L₂ is bonded preferably to the carbon atom at4-position which is indicated in formula (1c).

The nitrogen-containing aromatic heterocyclic derivative of theinvention is preferably represented by any one of formulae (2-1), (2-2),(3-1), (3-2), (4-1), (5-1), and (5-2), and particularly preferably byany one of formulae (2-1), (2-2), (3-2) and (5-2).

wherein R₁, R₂, R₃, R₄, a, b, c, d, e, X, and Q are as defined above.

Examples of the optional substituent when saying “substituted orunsubstituted” hereinbefore and hereinafter include a fluorine atom, acyano group, an alkyl group having 1 to 20, preferably 1 to 5 carbonatoms, a cycloalkyl group having 3 to 20, preferably 5 to 12 carbonatoms, an alkoxy group having 1 to 20, preferably 1 to 5 carbon atoms, ahaloalkyl group having 1 to 20, preferably 1 to 5 carbon atoms, ahaloalkoxy group having 1 to 20, preferably 1 to 5 carbon atoms, analkylsilyl group having 1 to 10, preferably 1 to 5 carbon atoms, an arylgroup having 6 to 30, preferably 6 to 18 ring carbon atoms, an aryloxygroup having 6 to 30, preferably 6 to 18 ring carbon atoms, an arylsilylgroup having 6 to 30, preferably 6 to 18 carbon atoms, an aralkyl grouphaving 7 to 30, preferably 7 to 20 carbon atoms, and a heteroaryl grouphaving 5 to 30, preferably 5 to 18 ring atoms.

Examples of the nitrogen-containing aromatic heterocyclic derivative areshown below, although not limited to the following compounds.

Organic EL Device

The organic EL device of the invention will be described below.

The organic EL device comprises organic thin film layers between thecathode the anode. The organic thin film layers comprise a lightemitting layer and at least one layer of the organic thin film layerscomprises the nitrogen-containing aromatic heterocyclic derivative ofthe invention mentioned above. By using the nitrogen-containing aromaticheterocyclic derivative of the invention in at least one layer of theorganic thin film layers, an organic EL device with high emissionefficiency and long lifetime is expected to obtain.

The organic thin film layer comprising the nitrogen-containing aromaticheterocyclic derivative of the invention may include a hole transportinglayer, a light emitting layer, a space layer, and a blocking layer,although not limited thereto. The nitrogen-containing aromaticheterocyclic derivative of the invention is preferably used in a holetransporting layer. The light emitting layer preferably comprises afluorescent material or a phosphorescent material, more preferablycomprises a phosphorescent material.

The organic EL device of the invention may be any of a single coloremitting device of fluorescent or phosphorescent type, a white-emittingdevice of fluorescent-phosphorescent hybrid type, an emitting device ofa simple type having a single emission unit, and an emitting device of atandem type having two or more emission units. The “emission unit”referred to herein is the smallest unit for emitting light by therecombination of injected holes and injected electrons, which comprisesone or more organic layers wherein at least one layer is a lightemitting layer.

Representative device structures of the simple-type organic EL deviceare shown below.

(1) Anode/Emission Unit/Cathode

The emission unit may be a laminate comprising two or more layersselected from a phosphorescent light emitting layer and a fluorescentlight emitting layer. A space layer may be disposed between the lightemitting layers to prevent the diffusion of excitons generated in thephosphorescent light emitting layer into the fluorescent light emittinglayer. Representative layered structures of the emission unit are shownbelow.

(a) hole transporting layer/light emitting layer (/electron transportinglayer);(b) hole transporting layer/first phosphorescent light emittinglayer/second phosphorescent light emitting layer (/electron transportinglayer);(c) hole transporting layer/phosphorescent light emitting layer/spacelayer/fluorescent light emitting layer (/electron transporting layer);(d) hole transporting layer/first phosphorescent light emittinglayer/second phosphorescent light emitting layer/space layer/fluorescentlight emitting layer (/electron transporting layer);(e) hole transporting layer/first phosphorescent light emittinglayer/space layer/second phosphorescent light emitting layer/spacelayer/fluorescent light emitting layer (/electron transporting layer);and(f) hole transporting layer/phosphorescent light emitting layer/spacelayer/first fluorescent light emitting layer/second fluorescent lightemitting layer (/electron transporting layer).

The emission color of the phosphorescent light emitting layer and thatof the fluorescent light emitting layer may be different. For example,the layered structure of the laminated light emitting layer (d) may behole transporting layer/first phosphorescent light emitting layer (redemission)/second phosphorescent light emitting layer (greenemission)/space layer/fluorescent light emitting layer (blueemission)/electron transporting layer.

An electron blocking layer may be disposed between the light emittinglayer and the hole transporting layer or between the light emittinglayer and the space layer, if necessary. Also, a hole blocking layer maybe disposed between the light emitting layer and the electrontransporting layer, if necessary. With such a electron blocking layer ora hole blocking layer, electrons and holes are confined in the lightemitting layer to increase the degree of charge recombination in thelight emitting layer, thereby improving the emission efficiency.

Representative device structure of the tandem-type organic EL device isshown below.

(2) Anode/First Emission Unit/Intermediate Layer/Second EmissionUnit/Cathode

The layered structure of the first emission unit and the second emissionunit may be selected from those described above with respect to theemission unit.

Generally, the intermediate layer is also called an intermediateelectrode, an intermediate conductive layer, a charge generation layer,an electron withdrawing layer, a connecting layer, or an intermediateinsulating layer. The intermediate layer may be formed by knownmaterials so as to supply electrons to the first emission unit and holesto the second emission unit.

A schematic structure of an example of the organic EL device of theinvention is shown in FIG. 1 wherein the organic EL device 1 comprises asubstrate 2, an anode 3, a cathode 4, and an emission unit 10 disposedbetween the anode 3 and the cathode 4. The emission unit 10 comprises alight emitting layer 5 which comprises at least one phosphorescentemitting layer containing a phosphorescent host material and aphosphorescent dopant. A hole transporting layer 6, etc. may be disposedbetween the light emitting layer 5 and the anode 3, and an electrontransporting layer 7, etc. may be disposed between the light emittinglayer 5 and the cathode 4. An electron blocking layer may be disposed onthe anode 3 side of the light emitting layer 5, and a hole blockinglayer may be disposed on the cathode 4 side of the light emitting layer5. With these blocking layers, electrons and holes are confined in thelight emitting layer 5 to increase the degree of exciton generation inthe light emitting layer 5.

In the present invention, the host is referred to as a fluorescent hostwhen combinedly used with a fluorescent dopant and as a phosphorescenthost when combinedly used with a phosphorescent dopant. Therefore, thefluorescent host and the phosphorescent host are not distinguished fromeach other merely by the difference in their molecular structures.Namely, the term “phosphorescent host” means a material for constitutinga phosphorescent emitting layer containing a phosphorescent dopant anddoes not mean that the material is not usable as a material forconstituting a fluorescent emitting layer. The same also applies to thefluorescent host.

Substrate

The organic EL device of the invention is formed on a light-transmissivesubstrate. The light-transmissive substrate serves as a support for theorganic EL device and preferably a flat substrate having a transmittanceof 50% or more to 400 to 700 nm visible light. Examples of the substrateinclude a glass plate and a polymer plate. The glass plate may include aplate made of soda-lime glass, barium-strontium-containing glass, leadglass, aluminosilicate glass, borosilicate glass, barium borosilicateglass, or quartz. The polymer plate may include a plate made ofpolycarbonate, acryl, polyethylene terephthalate, polyether sulfide, orpolysulfone.

Anode

The anode of the organic EL device injects holes to the holetransporting layer or the light emitting layer, and an anode having awork function of 4.5 eV or more is effective. Examples of material foranode include indium tin oxide alloy (ITO), tin oxide (NESA), indiumzinc oxide alloy, gold, silver, platinum, and cupper. The anode isformed by making the electrode material into a thin film by a method,such as a vapor deposition method or a sputtering method. When gettingthe light emitted from the light emitting layer through the anode, thetransmittance of anode to visible light is preferably more than 10%. Thesheet resistance of anode is preferably several hundreds Ω/□ or less.The film thickness of anode depends upon the kind of material andgenerally 10 nm to 1 μm, preferably 10 to 200 nm.

Cathode

The cathode injects electrons to the electron injecting layer, theelectron transporting layer or the light emitting layer, and preferablyformed from a material having a small work function. Examples of thematerial for cathode include, but not limited to, indium, aluminum,magnesium, magnesium-indium alloy, magnesium-aluminum alloy,aluminum-lithium alloy, aluminum-scandium-lithium alloy, andmagnesium-silver alloy. Like the anode, the cathode is formed by makingthe material into a thin film by a method, such as the vapor depositionmethod and the sputtering method. The emitted light may be taken fromthe cathode, if appropriate.

Light Emitting Layer

The light emitting layer is an organic layer having a light emittingfunction. A light emitting layer employing a doping system comprises ahost material and a dopant material, wherein the major function of thehost material is to promote the recombination of electrons and holes andconfine excitons in the light emitting layer, and the dopant materialcauses the excitons generated by recombination to emit lightefficiently.

In case of a phosphorescent device, the major function of the hostmaterial is to confine the excitons generated on the dopant in the lightemitting layer.

To control the carrier balance in the light emitting layer, a doublehost (host and co-host) system may be used for the light emitting layer,for example, by combinedly using an electron transporting host and ahole transporting host.

The light emitting layer may be made into a double dopant layer, inwhich two or more kinds of dopant materials having high quantum yieldare combinedly used and each dopant material emits light with its owncolor. For example, to obtain a yellow emission, a light emitting layerformed by co-depositing a host, a red-emitting dopant and agreen-emitting dopant is used.

In a laminate of two or more light emitting layers, electrons and holesare accumulated in the interface between the light emitting layers, andtherefore, the recombination region is localized in the interfacebetween the light emitting layers, to improve the quantum efficiency.

The light emitting layer may be different in the hole injection abilityand the electron injection ability, and also in the hole transportingability and the electron transporting ability each being expressed bymobility.

The light emitting layer is formed, for example, by a known method, suchas a vapor deposition method, a spin coating method, and LB method.Alternatively, the light emitting layer may be formed by making asolution of a binder, such as resin, and the material for the lightemitting layer in a solvent into a thin film by a method such as spincoating.

The light emitting layer is preferably a molecular deposit film. Themolecular deposit film is a thin film formed by depositing a vaporizedmaterial or a film formed by solidifying a material in the state ofsolution or liquid. The molecular deposit film can be distinguished froma thin film formed by LB method (molecular build-up film) by thedifferences in the assembly structures and higher order structures andthe functional difference due to the structural differences.

The phosphorescent dopant (phosphorescent emitting material) is acompound which emits light by releasing the energy of excited tripletstate and preferably a organometallic complex comprising at least onemetal selected from Ir, Pt, Os, Au, Cu, Re, and Ru and a ligand,although not particularly limited thereto as long as emitting light byreleasing the energy of excited triplet state. A ligand having an orthometal bond is preferred. In view of obtaining a high phosphorescentquantum yield and further improving the external quantum efficiency ofelectroluminescence device, a metal complex comprising a metal selectedfrom Ir, Os, and Pt is preferred, with iridium complex, osmium complex,and platinum being more preferred, iridium complex and platinum complexbeing still more preferred, and an ortho metallated iridium complexbeing particularly preferred.

The content of the phosphorescent dopant in the light emitting layer isnot particularly limited and selected according to the use of thedevice, and preferably 0.1 to 70% by mass, and more preferably 1 to 30%by mass. If being 0.1% by mass or more, the amount of light emission issufficient. If being 70% by mass or less, the concentration quenchingcan be avoided.

Preferred examples of the organometallic complex are shown below.

The phosphorescent host is a compound which confines the triplet energyof the phosphorescent dopant efficiently in the light emitting layer tocause the phosphorescent dopant to emit light efficiently. Thenitrogen-containing aromatic heterocyclic derivative of the invention isuseful as a phosphorescent host. If necessary, in addition to thenitrogen-containing aromatic heterocyclic derivative of the invention,another compound may be used as the phosphorescent host according to theuse of the device.

The nitrogen-containing aromatic heterocyclic derivative of theinvention and another compound may be combinedly used in the same lightemitting layer as the phosphorescent host material. If two or more lightemitting layers are formed, the nitrogen-containing aromaticheterocyclic derivative of the invention can be used in one of the lightemitting layers as the phosphorescent host material and a compound otherthan the nitrogen-containing aromatic heterocyclic derivative of theinvention can be used in another light emitting layer as thephosphorescent host material. The nitrogen-containing aromaticheterocyclic derivative of the invention may be used in an organic layerother than the light emitting layer. In this case, a compound other thanthe nitrogen-containing aromatic heterocyclic derivative of theinvention may be used as a phosphorescent host of the light emittinglayer.

Examples of the compounds other than the nitrogen-containing aromaticheterocyclic derivative of the invention, which are suitable as thephosphorescent host, include a carbazole derivative, a triazolederivative, a oxazole derivative, an oxadiazole derivative, an imidazolederivative, a polyarylalkane derivative, a pyrazoline derivative, apyrazolone derivative, a phenylenediamine derivative, an arylaminederivative, an amino-substituted chalcone derivative, a styrylanthracenederivative, a fluorenone derivative, a hydrazone derivative, a stilbenederivative, a silazane derivative, an aromatic tertiary amine compound,a styrylamine compound, an aromatic methylidene compound, a porphyrincompound, an anthraquinodimethane derivative, an anthrone derivative, adiphenylquinone derivative, a thiopyran dioxide derivative, acarbodiimide derivative, a fluorenylidenemethane derivative, adistyrylpyrazine derivative, a tetracarboxylic anhydride of fused ringsuch as naphthalene and perylene, a phthalocyanine derivative, a metalcomplex of 8-quinolinol derivative, metal phthalocyanine, metalcomplexes having a ligand such as benzoxazole and benzothiazole, anelectroconductive oligomer, such as a polysilane compound, apoly(N-vinylcarbazole) derivative, an aniline copolymer, thiopheneoligomer, and a polythiophene, and a polymer such as a polythiophenederivative, a polyphenylene derivative, a polyphenylenevinylenederivative, and a polyfluorene derivative. These phosphorescent hostsmay be used alone or in combination of two or more. Specific examplesthereof are shown below.

The thickness of the light emitting layer is preferably 5 to 50 nm, morepreferably 7 to 50 nm, and still more preferably 10 to 50 nm. If being 5nm or more, the light emitting layer is easily formed. If being 50 nm orless, the increase in driving voltage is avoided.

Electron-Donating Dopant

It is preferred for the organic EL device of the invention to contain anelectron-donating dopant in the interfacial region between the cathodeand the light emitting unit. With such a construction, the organic ELdevice has an improved luminance and an elongated lifetime. Theelectron-donating dopant is a metal having a work function of 3.8 eV orless or a compound containing such metal. Examples thereof include atleast one compound selected from alkali metal, alkali metal complex,alkali metal compound, alkaline earth metal, alkaline earth metalcomplex, alkaline earth metal compound, rare earth metal, rare earthmetal complex, and rare earth metal compound.

Examples of the alkali metal include Na (work function: 2.36 eV), K(work function: 2.28 eV), Rb (work function: 2.16 eV), and Cs (workfunction: 1.95 eV), with those having a work function of 2.9 eV or lessbeing particularly preferred. Of the above, preferred are K, Rb, and Cs,more preferred are Rb and Cs, and most preferred is Cs. Examples of thealkaline earth metal include Ca (work function: 2.9 eV), Sr (workfunction: 2.0 to 2.5 eV), and Ba (work function: 2.52 eV), with thosehaving a work function of 2.9 eV or less being particularly preferred.Examples of the rare earth metal include Sc, Y, Ce, Tb, and Yb, withthose having a work function of 2.9 eV or less being particularlypreferred.

Examples of the alkali metal compound include alkali oxide, such asLi₂O, Cs₂O, K₂O, and alkali halide, such as LiF, NaF, CsF, and KF, withLiF, Li₂O, and NaF being preferred. Examples of the alkaline earth metalcompound include BaO, SrO, CaO, and mixture thereof, such asBa_(x)Sr_(1-x)O (0<x<1) and Ba_(x)Ca_(1-x)O (0<x<1), with BaO, SrO, andCaO being preferred. Examples of the rare earth metal compound includeYbF₃, ScF₃, ScO₃, Y₂O₃, Ce₂O₃, GdF₃, and TbF₃, with YbF₃, ScF₃, and TbF₃being preferred.

Examples of the alkali metal complex, alkaline earth metal complex, andrare earth metal complex are not particularly limited as long ascontaining at least one metal ion selected from alkali metal ions,alkaline earth metal ions, rare earth metal ions, respectively. Theligand is preferably, but not limited to, quinolinol, benzoquinolinol,acridinol, phenanthridinol, hydroxyphenyloxazole, hydroxyphenylthiazole,hydroxydiaryloxadiazole, hydroxydiarylthiadiazole,hydroxyphenylpyridine, hydroxyphenylbenzimidazole, hydroxybenzotriazole,hydroxyfulborane, bipyridyl, phenanthroline, phthalocyanine, porphyrin,cyclopentadiene, β-diketones, azomethines, and derivative thereof.

The electron-donating dopant is added to the interfacial regionpreferably into a form of layer or island. The electron-donating dopantis added preferably by co-depositing the electron-donating dopant withthe organic compound (light emitting material, electron injectingmaterial, etc.) for forming the interfacial region by a resistanceheating deposition method, thereby dispersing the electron-donatingdopant into the organic material. The disperse concentration expressedby the molar ratio of the organic material and the electron-donatingdopant is 100:1 to 1:100 and preferably 5:1 to 1:5.

When the electron-donating dopant is formed into a form of layer, alight emitting material or an electron injecting material is made into alayer which serves as an organic layer in the interface, and then, theelectron-donating dopant alone is deposited by a resistance heatingdeposition method into a layer having a thickness preferably 0.1 to 15nm. When the electron-donating dopant is formed into a form of island, alight emitting material or an electron injecting material is made into aform of island which serves as an organic layer in the interface, andthen, the electron-donating dopant alone is deposited by a resistanceheating deposition method into a form of island having a thicknesspreferably 0.05 to 1 nm.

The molar ratio of the main component and the electron-donating dop antin the organic electroluminescence device of the invention is preferably5:1 to 1:5 and more preferably 2:1 to 1:2.

Electron Transporting Layer

The electron transporting layer is an organic layer disposed between thelight emitting layer and the cathode and transports electrons from thecathode to the light emitting layer. If two or more electrontransporting layers are provided, the organic layer closer to thecathode may be called an electron injecting layer in some cases. Theelectron injecting layer injects electrons from the cathode to theorganic layer unit efficiently.

An aromatic heterocyclic compound having one or more heteroatoms in itsmolecule is preferably used as the electron transporting material forthe electron transporting layer, with a nitrogen-containing ringderivative being particularly preferred. The nitrogen-containing ringderivative is preferably an aromatic ring compound having anitrogen-containing 6- or 5-membered ring or a condensed aromatic ringcompound having a nitrogen-containing 6- or 5-membered ring.

The nitrogen-containing ring derivative is preferably, for example, achelate metal complex having a nitrogen-containing ring represented byformula (A).

R² to R⁷ of formula (A) each independently represent a hydrogen atom, ahalogen atom, a hydroxyl group, an amino group, a hydrocarbon grouphaving 1 to 40 carbon atoms, an alkoxy group having 1 to 40 carbonatoms, an aryloxy group having 6 to 50 carbon atoms, an alkoxycarbonylgroup, or a heterocyclic group having 5 to 50 carbon atoms, each beingoptionally substituted.

The halogen atom may include fluorine, chlorine, bromine, and iodine.

The substituted amino group may include an alkylamino group, anarylamino group, and an aralkylamino group.

The alkylamino group and the aralkylamino group are represented by—NQ¹Q², wherein Q¹ and Q² each independently represent an alkyl grouphaving 1 to 20 carbon atoms or an aralkyl group having 1 to 20 carbonatoms. One of Q¹ and Q² may be a hydrogen atom.

The arylamino group is represented by —NAr¹Ar², wherein Ar¹ and Ar² eachindependently represent a non-condensed aromatic hydrocarbon group or acondensed aromatic hydrocarbon group each having 6 to 50 carbon atoms.One of Ar¹ and Ar² may be a hydrogen atom.

The hydrocarbon group having 1 to 40 carbon atoms may include an alkylgroup, an alkenyl group, a cycloalkyl group, an aryl group, and anaralkyl group.

The alkoxycarbonyl group is represented by —COOY′, wherein Y′ is analkyl group having 1 to 20 carbon atoms.

M represents aluminum (Al), gallium (Ga), or indium (In), with In beingpreferred.

L represents a group represented by formula (A′) or (A″):

R⁸ to R¹² in formula (A′) each independently represent a hydrogen atomor a substituted or unsubstituted hydrocarbon group having 1 to 40carbon atoms. The adjacent two groups may form a ring structure. R¹³ toR²⁷ in formula (A″) each independently represent a hydrogen atom or asubstituted or unsubstituted hydrocarbon group having 1 to 40 carbonatoms. The adjacent two groups may form a ring structure.

Examples of the hydrocarbon group having 1 to 40 carbon atoms for R⁸ toR¹² and R¹³ to R²⁷ in formulae (A′) and (A″) are the same as thosedescribed above with respect to R² to R⁷ of formula (A). Examples of thedivalent group formed by the adjacent two groups of R⁸ to R¹² and R¹³ toR²⁷ which completes the ring structure include tetramethylene group,pentamethylene group, hexamethylene group, diphenylmethane-2,2′-diylgroup, diphenylethane-3,3′-diyl group, and diphenylpropane-4,4′-diylgroup.

The electron transporting compound for the electron transporting layeris preferably a metal complex including 8-hydroxyquinoline or itsderivative, an oxadiazole derivative, and a nitrogen-containingheterocyclic derivative. Examples of the metal complex including8-hydroxyquinoline or its derivative include a metal chelate oxinoidincluding a chelated oxine (generally, 8-quinolinol or8-hydroxyquinoline), for example, tris(8-quinolinol)aluminum. Examplesof the oxadiazole derivative are shown below.

In the above formulae, each of Ar¹⁷, Ar¹⁸, Ar¹⁹, Ar²¹, Ar²², and Ar²⁵ isa substituted or unsubstituted aromatic hydrocarbon group or asubstituted or unsubstituted condensed aromatic hydrocarbon group eachhaving 6 to 50 carbon atoms, and Ar¹⁷ and Ar¹⁸, Ar¹⁹ and Ar²¹, and Ar²²and Ar²⁵ may be the same or different. Examples of the aromatichydrocarbon group and the condensed aromatic hydrocarbon group includephenyl group, naphthyl group, biphenyl group, anthranyl group, perylenylgroup, and pyrenyl group. The optional substituent may be an alkyl grouphaving 1 to 10 carbon atoms, an alkoxyl group having 1 to 10 carbonatoms or a cyano group.

Each of Ar²⁰, Ar²³, and Ar²⁴ is a substituted or unsubstituted divalentaromatic hydrocarbon group or a substituted or unsubstituted divalentcondensed aromatic hydrocarbon group each having 6 to 50 carbon atoms,and Ar²³ and Ar²⁴ may be the same or different. Examples of the divalentaromatic hydrocarbon group or the divalent condensed aromatichydrocarbon group include phenylene group, naphthylene group,biphenylene group, anthranylene group, perylenylene group, andpyrenylene group. The optional substituent may be an alkyl group having1 to 10 carbon atoms, an alkoxyl group having 1 to 10 carbon atoms or acyano group.

Electron transporting compounds which have a good thin film-formingproperty are preferably used. Examples of the electron transportingcompound are shown below.

Examples of the nitrogen-containing heterocyclic derivative for use asthe electron transporting compound include a nitrogen-containingheterocyclic derivative having the following formulae but exclusive ofmetal complex, for example, a compound having a 5- or 6-membered ringwhich has the skeleton represented by formula (B) or having thestructure represented by formula (C).

In formula (C), X is a carbon atom or a nitrogen atom. Z₁ and Z₂ eachindependently represent a group of atoms for completing thenitrogen-containing heteroring.

The nitrogen-containing heterocyclic derivative is more preferably anorganic compound which has a nitrogen-containing aromatic polycyclicring comprising a 5-membered ring or a 6-membered ring. Anitrogen-containing aromatic polycyclic compound having two or morenitrogen atoms which has a skeleton comprising (B) and (C) or a skeletoncomprising (B) and (D) is also preferred.

The nitrogen-containing group of the nitrogen-containing aromaticpolycyclic compound is selected, for example, from thenitrogen-containing heterocyclic groups shown below.

In the above formulae, R is an aromatic hydrocarbon group or a condensedaromatic hydrocarbon group each having 6 to 40 carbon atoms, an aromaticheterocyclic group or a condensed aromatic heterocyclic group eachhaving 3 to 40 carbon atoms, an alkyl group having 1 to 20 carbon atoms,or an alkoxy group having 1 to 20 carbon atoms; and n is an integer of 0to 5. If n is an integer of 2 or more, R groups may be the same ordifferent.

More preferred is a nitrogen-containing heterocyclic derivativerepresented by the following formula:

HAr-L¹-Ar¹-Ar²

wherein HAr is a substitute or unsubstituted nitrogen-containingheterocyclic group having 3 to 40 carbon atoms; L¹ is a single bond, asubstituted or unsubstituted aromatic hydrocarbon group or condensedaromatic hydrocarbon group each having 6 to 40 carbon atoms, or asubstituted or unsubstituted aromatic heterocyclic group or condensedaromatic heterocyclic group each having 3 to 40 carbon atoms; Ar¹ is asubstitute or unsubstituted divalent aromatic hydrocarbon group having 6to 40 carbon atoms; and Ar² is a substitute or unsubstituted aromatichydrocarbon group or condensed aromatic hydrocarbon group each having 6to 40 carbon atoms or a substituted or unsubstituted aromaticheterocyclic group or condensed aromatic heterocyclic group each having3 to 40 carbon atoms.

HAr is selected, for example, from the following groups:

L¹ is selected, for example, from the following groups:

Ar¹ is selected, for example, from the following arylanthranyl groups:

In the above formulae, R¹ to R¹⁴ are each independently a hydrogen atom,a halogen atom, an alkyl group having 1 to 20 carbon atoms, an alkoxygroup having 1 to 20 carbon atoms, an aryloxy group having 6 to 40carbon atoms, a substituted or unsubstituted aromatic hydrocarbon groupor condensed aromatic hydrocarbon group each having 6 to 40 carbonatoms, or a substituted or unsubstituted aromatic heterocyclic group orcondensed aromatic heterocyclic group each having 3 to 40 carbon atoms;and Ar³ is a substituted or unsubstituted aromatic hydrocarbon group orcondensed aromatic hydrocarbon group each having 6 to 40 carbon atoms ora substituted or unsubstituted aromatic heterocyclic group or condensedaromatic heterocyclic group each having 3 to 40 carbon atoms. R¹ to R⁸may be all hydrogen atoms.

Ar² is selected, for example, from the following groups:

In addition, the nitrogen-containing aromatic polycyclic compound foruse as the electron transporting compound further includes the followingcompound:

wherein R₁ to R₄ each independently represent a hydrogen atom, asubstituted or unsubstituted aliphatic group having 1 to 20 carbonatoms, a substituted or unsubstituted alicyclic group having 3 to 20carbon atoms, a substituted or unsubstituted aromatic group having 6 to50 carbon atoms, or a substituted or unsubstituted heterocyclic grouphaving 3 to 50 carbon atoms; and X₁ and X₂ each independently representan oxygen atom, a sulfur atom, or dicyanomethylene group.

Further, the following compound is also suitable as the electrontransporting compound:

wherein R¹, R², R³, and R⁴ may be the same or different and eachrepresents an aromatic hydrocarbon group or a condensed aromatichydrocarbon group each represented by the following formula:

wherein R⁵, R⁶, R⁷, R⁸, and R⁹ may be the same or different and eachrepresents a hydrogen atom, a saturated or unsaturated alkoxyl grouphaving 1 to 20 carbon atoms, a saturated or unsaturated alkyl grouphaving 1 to 20 carbon atoms, an amino group, or an alkylamino grouphaving 1 to 20 carbon atoms. At least one of R⁵, R⁶, R⁷, R⁸, and R⁹ is agroup other than a hydrogen atom.

Further, a polymer having the nitrogen-containing heterocyclic group orthe nitrogen-containing heterocyclic derivative is also usable as theelectron transporting compound.

It is particularly preferred for the electron transporting layer of theorganic EL of the invention to contain at least one of thenitrogen-containing heterocyclic derivatives represented by thefollowing formulae (60) to (62).

In the formulae (60) to (62), Z¹, Z², and Z³ each independentlyrepresent a nitrogen atom or a carbon atom.

R¹ and R² each independently represent a substituted or unsubstitutedaryl group having 6 to 50 ring carbon atoms, a substituted orunsubstituted heteroaryl group having 5 to 50 ring atoms, a substitutedor unsubstituted alkyl group having 1 to 20 carbon atoms, a substitutedor unsubstituted haloalkyl group having 1 to 20 carbon atoms, or asubstituted or unsubstituted alkoxyl group having 1 to 20 carbon atoms.

The subscript n is an integer of 0 to 5. If n is an integer of 2 ormore, R¹ groups may be the same or different from each other. Theadjacent two R¹ groups may bond to each other to form a substituted orunsubstituted hydrocarbon ring.

Ar¹ represents a substituted or unsubstituted aryl group having 6 to 50ring carbon atoms or a substituted or unsubstituted heteroaryl grouphaving 5 to 50 ring atoms.

Ar² represents a hydrogen atom, a substituted or unsubstituted alkylgroup having 1 to 20 carbon atoms, a substituted or unsubstitutedhaloalkyl group having 1 to 20 carbon atoms, a substituted orunsubstituted alkoxyl group having 1 to 20 carbon atoms, a substitutedor unsubstituted aryl group having 6 to 50 ring carbon atoms, or asubstituted or unsubstituted heteroaryl group having 5 to 50 ring atoms.

However, one of Ar¹ and Ar² is a substituted or unsubstituted condensedaromatic hydrocarbon group having 10 to 50 ring carbon atoms or asubstituted or unsubstituted condensed aromatic heterocyclic grouphaving 9 to 50 ring atoms.

Ar³ represents a substituted or unsubstituted arylene group having 6 to50 ring carbon atoms or a substituted or unsubstituted heteroarylenegroup having 5 to 50 ring atoms.

L¹, L², and L³ each independently represent a single bond, a substitutedor unsubstituted arylene group having 6 to 50 ring carbon atoms or asubstituted or unsubstituted divalent condensed aromatic heterocyclicgroup having 9 to 50 ring atoms.

Examples of the aryl group having 6 to 50 ring carbon atoms includephenyl group, naphthyl group, anthryl group, phenanthryl group,naphthacenyl group, chrysenyl group, pyrenyl group, biphenyl group,terphenyl group, tolyl group, fluoranthenyl group, and fluorenyl group.

Examples of the heteroaryl group having 5 to 50 ring atoms includepyrrolyl group, furyl group, thienyl group, silolyl group, pyridylgroup, quinolyl group, isoquinolyl group, benzofuryl group, imidazolylgroup, pyrimidyl group, carbazolyl group, selenophenyl group,oxadiazolyl group, triazolyl group, pyrazinyl group, pyridazinyl group,triazinyl group, quinoxalinyl group, acridinyl group,imidazo[1,2-a]pyridinyl group, and imidazo[1,2-a]pyrimidinyl.

Examples of the alkyl group having 1 to 20 carbon atoms include methylgroup, ethyl group, propyl group, butyl group, pentyl group, and hexylgroup.

Examples of the haloalkyl group having 1 to 20 carbon atoms include thegroups obtained by replacing one or more hydrogen atoms of the alkylgroup mentioned above with at least one halogen atom selected fromfluorine, chlorine, iodine, and bromine.

Examples of the alkyl moiety of the alkoxyl group having 1 to 20 carbonatoms include the alkyl group mentioned above.

Examples of the arylene group having 6 to 50 ring carbon atoms includethe groups obtained by removing one hydrogen atom from the aryl groupmentioned above.

Examples of the divalent condensed aromatic heterocyclic group having 9to 50 ring atoms include the groups obtained by removing one hydrogenatom from the condensed aromatic heterocyclic group mentioned above asthe heteroaryl group.

The thickness of the electron transporting layer is preferably 1 to 100nm, although not particularly limited thereto.

The electron injecting layer which may be formed adjacent to theelectron transporting layer preferably comprises an inorganic compound,such as an insulating material and a semiconductor, in addition to thenitrogen-containing ring derivative. The insulating material orsemiconductor incorporated into the electron injecting layer effectivelyprevents the leak of electric current to enhance the electron injectingproperties.

The insulating material is preferably at least one metal compoundselected from the group consisting of alkali metal chalcogenides,alkaline earth metal chalcogenides, alkali metal halides and alkalineearth metal halides. The alkali metal chalcogenide, etc. incorporatedinto the electron injecting layer further enhances the electroninjecting properties. Preferred examples of the alkali metalchalcogenides include Li₂O, K₂O, Na₂S, Na₂Se and Na₂O, and preferredexamples of the alkaline earth metal chalcogenides include CaO, BaO,SrO, BeO, BaS and CaSe. Preferred examples of the alkali metal halidesinclude LiF, NaF, KF, LiCl, KCl and NaCl. Examples of the alkaline earthmetal halides include fluorides such as CaF₂, BaF₂, SrF₂, MgF₂ and BeF₂and halides other than fluorides.

Examples of the semiconductor may include oxide, nitride or oxynitrideeach containing at least one element selected from the group consistingof Ba, Ca, Sr, Yb, Al, Ga, In, Li, Na, Cd, Mg, Si, Ta, Sb and Zn. Thesemiconductor may be used singly or in combination of two or more. Theinorganic compound forming the electron injecting layer preferably formsa microcrystalline or amorphous insulating thin film. When the electroninjecting layer is formed from such an insulating thin film, the thinfilm is made more uniform to decrease the pixel defects such as darkspots. Examples of such inorganic compound include alkali metalchalcogenides, alkaline earth metal chalcogenides, alkali metal halidesand alkaline earth metal halide, each being described above.

The thickness of the layer including the insulating material or thesemiconductor is preferably about 0.1 to 15 nm. The electron injectinglayer may be included with the electron-donating dopant described above.

Hole Transporting Layer

The hole transporting layer is an organic layer formed between the lightemitting layer and the anode and has a function of transporting holesfrom the anode to the light emitting layer. When the hole transportinglayer is formed by two or more layers, the layer closer to the anode maybe defined as the hole injecting layer in some cases. The hole injectinglayer has a function of efficiently injecting holes from the anode tothe organic layer unit.

An aromatic amine compound, for example, the aromatic amine derivativerepresented by formula (I), is also preferably used as the material forforming the hole transporting layer.

In the formula (I), each of Ar¹ to Ar⁴ represents a substituted orunsubstituted aromatic hydrocarbon group or condensed aromatichydrocarbon group having 6 to 50 ring carbon atoms, a substituted orunsubstituted aromatic heterocyclic group or condensed aromaticheterocyclic group having 5 to 50 ring atoms, or a group wherein thearomatic hydrocarbon group or condensed aromatic hydrocarbon group andthe aromatic heterocyclic group or condensed aromatic heterocyclic groupare boned to each other.

L represents a substituted or unsubstituted aromatic hydrocarbon groupor condensed aromatic hydrocarbon group each having 6 to 50 ring carbonatoms or a substituted or unsubstituted aromatic heterocyclic group orcondensed aromatic heterocyclic group each having 5 to 50 ring atoms.

Specific examples of the compound represented by the formula (I) areshown below.

The aromatic amine represented by the formula (II) is also preferablyused as the material for forming the hole transporting layer.

In the formula (II), each of Ar¹ to Ar³ is defined in the same manner asin the definition of Ar¹ to Ar⁴ of the formula (I). The specificexamples of the compounds represented by the formula (II) are shownbelow, although not limited thereto.

The hole transporting layer of the organic EL device of the inventionmay be made into two-layered structure of a first hole transportinglayer (anode side) and a second hole transporting layer (cathode side).

The thickness of the hole transporting layer is preferably 10 to 200 nm,although not particularly limited thereto.

The organic EL device of the invention may have a layer comprising anelectron accepting compound which is attached to the anode side of eachof the hole transporting layer and the first hole transporting layer.With such a layer, it is expected that the driving voltage is loweredand the production cost is reduced.

The electron accepting compound is preferably a compound represented byformula (A):

wherein R²¹ to R²⁶ may be the same or different and each independentlyrepresent a cyano group, —CONH₂, a carboxyl group, or —COOR²⁷ whereinR²⁷ represents an alkyl group having 1 to 20 carbon atoms or acycloalkyl group having 3 to 20 carbon atoms. One or more of a pair ofR²¹ and R²², a pair of R²³ and R²⁴, and a pair of R²⁵ and R²⁶ may bondto each other to form a group represented by —CO—O—CO—.

Examples of R²⁷ include methyl group, ethyl group, n-propyl group,isopropyl group, n-butyl group, isobutyl group, t-butyl group,cyclopentyl group, and cyclohexyl group.

The thickness of the layer comprising the electron accepting compound ispreferably 5 to 20 nm, although not particularly limited thereto.

N/P Doping

The carrier injecting properties of the hole transporting layer and theelectron transporting layer can be controlled by, as described in JP3695714B, the doping (n) with a donor material or the doping (p) with anacceptor material.

A typical example of the n-doping is an electron transporting materialdoped with a metal, such as Li and Cs, and a typical example of thep-doping is a hole transporting material doped with an acceptormaterial, such as F₄TCNQ.

Space Layer

For example, in an organic EL device wherein a fluorescent lightemitting layer and a phosphorescent light emitting layer are laminated,a space layer is disposed between the fluorescent light emitting layerand the phosphorescent light emitting layer to prevent the diffusion ofexcitons generated in the phosphorescent light emitting layer to thefluorescent light emitting layer or to control the carrier balance. Thespace layer may be disposed between two or more phosphorescent lightemitting layers.

Since the space layer is disposed between the light emitting layers, amaterial combining the electron transporting ability and the holetransporting ability is preferably used for forming the space layer. Toprevent the diffusion of triplet energy in the adjacent phosphorescentlight emitting layer, the triplet energy of the material for the spacelayer is preferably 2.6 eV or more. The materials described with respectto the hole transporting layer are usable as the material for the spacelayer.

Blocking Layer

The organic EL device of the invention preferably has a blocking layer,such as an electron blocking layer, a hole blocking layer, and a tripletblocking layer, which is disposed adjacent to the light emitting layer.The electron blocking layer is a layer which prevents the diffusion ofelectrons from the light emitting layer to the hole transporting layer.The hole blocking layer is a layer which prevents the diffusion of holesfrom the light emitting layer to the electron transporting layer.

The triplet blocking layer, as mentioned below, prevents the diffusionof triplet excitons generated in the light emitting layer to adjacentlayers and has a function of confining the triplet excitons in the lightemitting layer, thereby preventing the deactivation of energy onmolecules other than the emitting dopant of triplet excitons, forexample, on molecules in the electron transporting layer.

If a device having a triplet blocking layer satisfies the followingenergy relationship:

E ^(T) _(d) <E ^(T) _(TB)

wherein E^(T) _(d) is the triplet energy of the phosphorescent dopant inthe light emitting layer and E^(T) _(TB) is the triplet energy of thecompound forming the triplet blocking layer,the triplet excitons of phosphorescent dopant are confined (not diffuseto other molecules). Therefore, the energy deactivation process otherthan the emission on the phosphorescent dopant may be prevented to causethe emission with high efficiency. However, even in case of satisfyingthe relationship of E^(T) _(d)<E^(T) _(TB), the triplet excitons maymove into other molecules if the energy difference (ΔE^(T)=E^(T)_(TB)−E^(T) _(d)) is small, because the energy difference ΔE^(T) may beovercome by the absorption of ambient heat energy when driving a deviceat around room temperature as generally employed in practical drive ofdevice. As compared with the fluorescent emission, the phosphorescentemission is relatively likely to be affected by the diffusion ofexcitons due to the heat absorption because the lifetime of tripletexcitons is longer. Therefore, as for the energy difference ΔE^(T), thelarger as compared with the heat energy of room temperature, the better.The energy difference ΔE^(T) is more preferably 0.1 eV or more andparticularly preferably 0.2 eV or more.

The triplet energy referred to herein was determined as follows.

A sample was dissolved in EPA solvent (diethylether:isopentane:ethanol=5:5:2 (by volume)) in a concentration of 10μmol/L to prepare a specimen for phosphorescence measurement. Thespecimen for phosphorescence measurement was placed in a quartz cell andirradiated with excitation ray at 77 K, and the emitted phosphorescencewas measured. Using the measured result, the triplet energy wasdetermined as the value calculated from the following conversionformula:

E ^(T) (eV)=1239.85/λ_(edge)

wherein λ_(edge) is determined as follows.

On the phosphorescence spectrum with a vertical axis of phosphorescentintensity and a horizontal axis of wavelength, a line tangent to therising portion at the short-wavelength side of the phosphorescentspectrum was drawn, and the wavelength (nm) at the intersection of thetangent line and the horizontal axis was expressed by “λ_(edge).”

A material satisfying the following relationship:

A _(b) −A _(h)≦0.1 eV

wherein A_(b) is the affinity of the blocking layer material and A_(h)is the affinity of the host material in the light emitting layer,is preferably used as the host material in the light emitting layer.

The electron affinity is defined as the amount of energy released orabsorbed when one electron is added to a molecule. The affinity level isexpressed by a positive sign when the energy is released and a negativesign when the energy is absorbed. Using the ionization potential Ip andthe optical energy gap Eg(S), the affinity Af is expressed by:

Af=Ip−Eg(S).

The ionization potential Ip is the amount of energy required to removean electron from a compound to ionize the compound. In the presentinvention, Ip is a positive value measured by a photoelectronicspectrophotometer (AC-3, manufactured by Riken Keiki Co., Ltd.) in theatmosphere. The optical energy gap Eg(S) is the difference between theconduction level and the valence level. In the present invention, Eg(S)is a positive value which is determined by measuring anultraviolet/visible absorption spectrum of a diluted dichloromethanesolution of a material, drawing a line tangent to the spectrum at thelong-wavelength side, and converting the wavelength of the intersectionbetween the tangent line and the base line (zero absorption) to the unitof energy.

The electron mobility of the material for the triplet blocking layer ispreferably 10⁻⁶ cm²/Vs or more at an electric field strength in a rangeof 0.04 to 0.5 MV/cm. There are several methods for measuring theelectron mobility of organic material, for example, Time of Flightmethod. In the present invention, the electron mobility is determined byimpedance spectroscopy.

The electron mobility of the electron injecting layer is preferably 10⁻⁶cm²/Vs or more at an electric field strength in a range of 0.04 to 0.5MV/cm. Within the above range, the injection of electrons from thecathode to the electron transporting layer is promoted and the injectionof electrons to the adjacent blocking layer and light emitting layer isalso promoted, thereby enabling to drive a device at lower voltage.

EXAMPLES

The present invention will be described in more detail with reference tothe examples. However, it should be noted that the scope of theinvention is not limited to the following examples.

Intermediate Synthesis 1-1: Synthesis of Intermediate 1-1

In an argon atmosphere, 23 g (90.6 mmol) of iodine, 9.4 g (41.2 mmol) ofperiodic acid dihydrate, 42 ml of water, 360 ml of acetic acid, and 11ml of sulfuric acid were added to 55 g (201.3 mmol) of2-bromo-9,9-dimethylfluorene, and the resultant mixture was stirred at65° C. for 30 min and further stirred at 90° C. for 6 h.

After the reaction, the reaction product was poured into iced water. Theprecipitated crystals were collected by filtration and washed with waterand then with methanol, to obtain 61 g of a white solid, which wasidentified as the following intermediate 1-1 by FD-MS analysis (yield:76%).

Intermediate Synthesis 1-2: Synthesis of Intermediate 1-2

In a nitrogen atmosphere, 150 g (0.89 mol) of dibenzofuran was dissolvedin 1000 ml of acetic acid under heating. After adding 188 g (1.18 mol)of bromine dropwise, the resultant mixture was stirred at roomtemperature for 20 h. The precipitated crystals were collected byfiltration and successively washed with acetic acid and water. The crudeproduct was recrystallized from methanol several times, to obtain 66.8 gof a white crystal, which was identified as the following intermediate1-2 by FD-MS analysis (yield: 30%).

Intermediate Synthesis 1-3: Synthesis of Intermediate 1-3

In an argon atmosphere, 400 ml of dehydrated THF was added to 24.7 g(100.0 mmol) of intermediate 1-2, and the resultant mixture was cooledto −40° C. Then 63 ml (100.0 mmol) of a 1.6 M hexane solution ofn-butyllithium was gradually added. After stirring the reaction solutionfor one hour while heating to 0° C., the reaction solution was againcooled to −78° C. and added dropwise with 26.0 g (250.0 mmol) of asolution of trimethyl borate in 50 ml of dehydrated THF. After thedropwise addition, the reaction solution was stirred at room temperaturefor 5 h. After adding 200 ml of a 1 N hydrochloric acid, the stirringwas further continued for one hour, and then, the water layer wasremoved. The organic layer was dried over MgSO₄ and the solvent wasremoved by evaporation under reduced pressure. The obtained solid waswashed with toluene, to obtain 15.2 g of a white crystal (yield: 72%).

Intermediate Synthesis 1-4: Synthesis of Intermediate 1-4

In an argon atmosphere, 150 ml of toluene, 150 ml of dimethoxyethane,and 150 ml (300.0 mmol) of a 2 M aqueous solution of Na₂CO₃ were addedto a mixture of 28.3 g (100.0 mmol) of 4-iodobromobenzene, 22.3 g (105.0mmol) of intermediate 1-3 and 2.31 g (2.00 mmol) of Pd[PPh₃]₄, and theresultant mixture was stirred for 10 h while refluxing under heating.

After the reaction, the reaction product was extracted withdichloromethane in a separatory funnel. The organic layer was dried overMgSO₄, filtered, and then concentrated. The concentrate was purified bysilica gel column chromatography, to obtain 24.2 g of a white solid,which was identified as the following intermediate 1-4 by FD-MS analysis(yield: 75%).

Intermediate Synthesis 1-5: Synthesis of Intermediate 1-5

In an argon atmosphere, 150 ml of toluene, 150 ml of dimethoxyethane,and 150 ml (300.0 mmol) of a 2 M aqueous solution of Na₂CO₃ were addedto a mixture of 28.3 g (100.0 mmol) of 4-iodobromobenzene, 22.3 g (105.0mmol) of dibenzofuran-4-boronic acid and 2.31 g (2.00 mmol) ofPd[PPh₃]₄, and the resultant mixture was stirred for 10 h whilerefluxing under heating.

After the reaction, the reaction product extracted with dichloromethanein a separatory funnel. The organic layer was dried over MgSO₄,filtered, and then concentrated. The concentrate was purified by silicagel column chromatography, to obtain 26.2 g of a white solid, which wasidentified as the following intermediate 1-5 by FD-MS analysis (yield:81%).

Intermediate Synthesis 1-6: Synthesis of Intermediate 1-6

The reaction of Intermediate Synthesis 1-5 was repeated except for using39.9 g of intermediate 1-1 in place of 4-iodobromobenzene, to obtain35.7 g of a white solid, which was identified as the followingintermediate 1-6 by FD-MS analysis (yield: 81%).

Intermediate Synthesis 1-7: Synthesis of Intermediate 1-7

Into a mixture of 17.7 g (72.7 mmol) of 9-phenylcarbazole, 6.03 g (36.3mmol) of potassium iodide and 7.78 g (36.4 mmol) of potassium iodate,5.9 ml of sulfuric acid and 70 ml of ethanol were added, and theresultant mixture was stirred at 75° C. for 2 h. After cooling, thereaction production was added with water and ethyl acetate andliquid-liquid extracted. The organic layer was washed with an aqueoussolution of sodium hydrogencarbonate and water and then concentrated.The obtained crude product was purified by silica gel columnchromatography, to obtain 21.8 g of a white solid, which was identifiedas the following intermediate 1-7 by FD-MS analysis (yield: 81%).

Intermediate Synthesis 1-8: Synthesis of Intermediate 1-8

In an argon atmosphere, 50 ml of dehydrated toluene and 50 ml ofdehydrated ether were added to 13.1 g (35.5 mmol) of intermediate 1-7,and the resultant mixture was cooled to −45° C. The mixture was furtheradded with 25 ml (39.5 mmol) of a 1.58 M hexane solution ofn-butyllithium and heated to −5° C. over one hour under stirring. Themixture was again cooled to −45° C. and added with 25 ml (109.0 mmol) oftriisopropyl borate dropwise to allow the reaction to proceed for 2 h.

After returning to room temperature, the reaction product was added witha 10% diluted hydrochloric acid and stirred for extraction. The organiclayer was washed with a saturated saline solution, dried over MgSO₄, andfiltered. The filtrate was concentrated, and the concentrate waspurified by silica gel column chromatography. The obtained solid waswashed with n-hexane, to obtain 7.1 g of a white solid (yield: 70%).

Intermediate Synthesis 1-9: Synthesis of Intermediate 1-9

In an argon atmosphere, 600 ml of dehydrated tetrahydrofuran was addedto 78.0 g (0.46 mol) of dibenzofuran. The resultant mixture was cooledto −30° C. and added with 300 ml (0.50 mol) of a 1.65 M hexane solutionof n-butyllithium dropwise, and then, the temperature was raised to roomtemperature over one hour under stirring. After further stirring at roomtemperature for 5 h, the mixture was cooled to −60° C. and added with 60ml (0.70 mol) of 1,2-dibromoethane dropwise over one hour.

After further stirring at room temperature for 15 h, the mixture waspoured into 1000 ml of iced water and then extracted withdichloromethane. The organic layer was washed with a saturated salinesolution, dried over MgSO₄, filtered, and then concentrated. Theconcentrate was purified by silica gel chromatography and washed withtetrahydrofuran/methanol, to obtain 70 g of solid, which was identifiedas the following intermediate 1-9 by FD-MS analysis (yield: 62%).

Intermediate Synthesis 2-1: Synthesis of Intermediate 2-1

In an argon atmosphere, 90 ml of dehydrated 1,4-dioxane was added to amixture of 15.0 g (58.5 mmol) of indolo[2,3-a]carbazole (synthesizedaccording to the method of Synlett p. 42-48 (2005)), 11.9 g (58.5 mmol)of iodobenzene, 11.2 g (58.5 mmol) of copper iodide, 20.0 g (175.5 mmol)of trans-1,2-cyclohexanediamine, and 37.3 g (175.5 mmol) of tripotassiumphosphate, and the resultant mixture was stirred for 24 h whilerefluxing under heating. The reaction solution was concentrated underreduced pressure. The obtained residue was added with 500 ml of toluene,heated to 120° C., and then filtered to remove insolubles. The filtratewas concentrated under reduced pressure and the obtained residue waspurified by silica gel column chromatography, to obtain 10.0 g of whitesolid, which was identified as the following intermediate 2-1 by FD-MSanalysis (yield: 51%).

Intermediate Synthesis 2-2: Synthesis of Intermediate 2-2

A solution of 25.0 g (101.5 mmol) of 3,3-methylenediindole and 15.1 g(101.5 mmol) of triethyl orthoformate in 400 ml of methanol was addedwith 1.4 ml of concentrated sulfuric acid and stirred for 5 h whilerefluxing under heating. The reaction solution was cooled in an icedwater bath. The precipitate was collected by filtration and washed with500 ml of methanol, to obtain 19.0 g of brown solid, which wasidentified as the following intermediate 2-2 by FD-MS analysis (yield:73%).

Intermediate Synthesis 2-3: Synthesis of Intermediate 2-3

In an argon atmosphere, 50 ml of dehydrated 1,4-dioxane was added to amixture of 5.1 g (20.0 mmol) of intermediate 2-2, 4.1 g (20.0 mmol) ofiodobenzene, 3.8 g (20.0 mmol) of copper iodide, 6.9 g (60.0 mmol) oftrans-1,2-cyclohexanediamine, and 12.7 g (60.0 mmol) of tripotassiumphosphate. The resultant mixture was stirred for 48 h while refluxingunder heating. The reaction solution was concentrated under reducedpressure. The obtained residue was added with 1000 ml of toluene, heatedto 120° C., and then filtered to remove the insolubles. The filtrate wasconcentrated under reduced pressure and the obtained residue waspurified by silica gel column chromatography, to obtain 1.7 g of brownsolid, which was identified as the following intermediate 2-3 by FD-MSanalysis (yield: 26%).

Intermediate Synthesis 2-4: Synthesis of Intermediate 2-4

In an argon atmosphere, 124 ml (248 mmol) of a 2 M aqueous solution ofNa₂CO₃, 250 ml of DME, 250 ml of toluene, and 7.2 g (6.2 mmol) ofPd[PPh₃]₄ were added to a mixture of 25.0 g (123.8 mmol) of2-bromonitrobenzene, 31.5 g (148.5 mmol) of 4-dibenzofuranboronic acid.The resultant mixture was stirred for 12 h while refluxing underheating.

After the reaction, the mixture was cooled to room temperature. Thereaction product was added with 500 ml of water and extracted withdichloromethane in a separatory funnel. The organic layer was dried overMgSO₄, filtered, and concentrated. The concentrate was purified bysilica gel column chromatography, to obtain 24.0 g of white solid, whichwas identified as the following intermediate 2-4 by FD-MS analysis(yield: 67%).

Intermediate Synthesis 2-5: Synthesis of Intermediate 2-5

In an argon atmosphere, 166 ml of dimethylacetamide was added to amixture of 24.0 g (83.0 mmol) of intermediate 2-4 and 54.4 g (207.4mmol) of triphenylphosphine. The resultant mixture was stirred for 20 hwhile refluxing under heating.

After the reaction, the mixture was cooled to room temperature. Thereaction product was added with 400 ml of water and extracted withdichloromethane in a separatory funnel. The organic layer was dried overMgSO₄, filtered and concentrated. The concentrate was purified by silicagel column chromatography, to obtain 14.5 g of white solid, which wasidentified as the following intermediate 2-5 by FD-MS analysis (yield:68%).

Intermediate Synthesis 2-6: Synthesis of Intermediate 2-6

The reaction of Intermediate Synthesis 2-4 was repeated except for using33.9 g of 4-dibenzothiopheneboronic acid in place of4-dibenzofuranboronic acid, to obtain 28.4 g of white powder, which wasidentified as the following intermediate 2-6 by FD-MS analysis (yield:75%).

Intermediate Synthesis 2-7: Synthesis of Intermediate 2-7

The reaction of Intermediate Synthesis 2-5 was repeated except for using25.3 g of intermediate 2-5 in place of intermediate 2-4, to obtain 14.7g of white powder, which was identified as the following intermediate2-7 by FD-MS analysis (yield: 65%).

Intermediate Synthesis 2-8: Synthesis of Intermediate 2-8

A solution of 18.7 g (142.0 mmol) of 1-indanone and 20.5 g (142.0 mmol)of phenylhydrazinium chloride in 400 ml of ethanol was added with 2.0 mlof concentrated sulfuric acid. The resultant mixture was stirred for 8 hwhile refluxing under heating. The reaction solution was allowed tostand for cooling, and then, the precipitate was collected by filtrationand washed with 500 ml of methanol. By recrystallizing the crudeproduct, 17.5 g of white solid was obtained, which was identified as thefollowing intermediate 2-8 by FD-MS analysis (yield: 60%).

Intermediate Synthesis 2-9: Synthesis of Intermediate 2-9

A solution of 18.7 g (142.0 mmol) of 1-indanone and 31.7 g (142.0 mmol)of 4-bromophenylhydrazine hydrochloride in 400 ml of ethanol was addedwith 2.0 ml of concentrated sulfuric acid. The resultant mixture wasstirred for 8 h while refluxing under heating. The reaction solution wasallowed to stand for cooling, and then, the precipitate was collected byfiltration and washed with 500 ml of methanol. By recrystallizing thecrude product, 21.7 g of white solid was obtained, which was identifiedas the following intermediate 2-9 by FD-MS analysis (yield: 54%).

Synthesis Example 1 Production of Aromatic Heterocyclic Derivative (H1)

In an argon atmosphere, 50 ml of dehydrated xylene was added to amixture of 3.2 g (10.0 mmol) of intermediate 1-5, 3.3 g (10.0 mmol) ofintermediate 2-1, 0.14 g (0.15 mmol) of Pd₂(dba)₃, 0.087 g (0.3 mmol) ofP(tBu)₃HBF₄, and 1.9 g (20.0 mmol) of sodium t-butoxide. The resultantmixture was refluxed for 8 h under heating.

After the reaction, the reaction solution was cooled to 50° C. andfiltered through celite and silica gel. The filtrate was concentratedand the obtained concentrate was purified by silica gel columnchromatography, to obtain a white solid. The crude product wasrecrystallized from toluene, to obtain 2.9 g of white crystal, which wasidentified as the following aromatic heterocyclic derivative (H1) byFD-MS analysis (yield: 50%).

Synthesis Example 2 Production of Aromatic Heterocyclic Derivative (H12)

The reaction of Synthesis Example 1 was repeated except for using 3.2 gof intermediate 1-4 in place of intermediate 1-5, to obtain 3.0 g ofwhite crystal, which was identified as the following aromaticheterocyclic derivative (H2) by FD-MS analysis (yield: 52%).

Synthesis Example 3 Production of Aromatic Heterocyclic Derivative (H3)

The reaction of Synthesis Example 1 was repeated except for using 4.4 gof intermediate 1-6 in place of intermediate 1-5, to obtain 3.7 g ofwhite crystal, which was identified as the following aromaticheterocyclic derivative (H3) by FD-MS analysis (yield: 54%).

Synthesis Example 4 Production of Aromatic Heterocyclic Derivative (H4)

The reaction of Synthesis Example 1 was repeated except for using 3.3 gof intermediate 2-3 in place of intermediate 2-1, to obtain 3.0 g ofwhite crystal, which was identified as the following aromaticheterocyclic derivative (H4) by FD-MS analysis (yield: 50%).

Synthesis Example 5 Production of Aromatic Heterocyclic Derivative (H5)

The reaction of Synthesis Example 1 was repeated except for using 3.2 gof intermediate 1-4 in place of intermediate 1-5 and using 3.3 g ofintermediate 2-3 in place of intermediate 2-1, to obtain 2.9 g of whitecrystal, which was identified as the following aromatic heterocyclicderivative (H5) by FD-MS analysis (yield: 50%).

Synthesis Example 6 Production of Aromatic Heterocyclic Derivative (H6)

The reaction of Synthesis Example 1 was repeated except for using 4.4 gof intermediate 1-6 in place of intermediate 1-5 and using 3.3 g ofintermediate 2-3 in place of intermediate 2-1, to obtain 3.2 g of whitecrystal, which was identified as the following aromatic heterocyclicderivative (H6) by FD-MS analysis (yield: 46%).

Synthesis Example 7 Production of Aromatic Heterocyclic Derivative (H7)

The reaction of Synthesis Example 1 was repeated except for using 4.4 gof intermediate 1-6 in place of intermediate 1-5 and using 2.6 g ofintermediate 2-5 in place of intermediate 2-1, to obtain 3.1 g of whitecrystal, which was identified as the following aromatic heterocyclicderivative (H7) by FD-MS analysis (yield: 50%).

Synthesis Example 8 Production of Aromatic Heterocyclic Derivative (H8)

The reaction of Synthesis Example 1 was repeated except for using 4.4 gof intermediate 1-6 in place of intermediate 1-5 and using 2.7 g ofintermediate 2-7 in place of intermediate 2-1, to obtain 3.0 g of whitecrystal, which was identified as the following aromatic heterocyclicderivative (H8) by FD-MS analysis (yield: 47%).

Synthesis Example 9 Production of Aromatic Heterocyclic Derivative (H9)

In an argon atmosphere, 50 ml of dehydrated 1,4-dioxane was added to amixture of 8.8 g (20.0 mmol) of intermediate 1-6, 4.1 g (20.0 mmol) ofintermediate 2-8, 3.8 g (20.0 mmol) of copper iodide, 6.9 g (60.0 mmol)of trans-1,2-cyclohexanediamine, and 12.7 g (60.0 mmol) of tripotassiumphosphate. The resultant mixture was stirred for 48 h while refluxingunder heating. The reaction solution was concentrated under reducedpressure. The obtained residue was added with 1000 ml of toluene, heatedto 120° C., and filtered to remove the insolubles. The filtrate wasconcentrated under reduced pressure, and the obtained residue waspurified by silica gel column chromatography, to obtain 6.0 g of whitesolid, which was identified as the following intermediate (9-a) by FD-MSanalysis.

A mixture of 5.6 g (50.0 mmol) of potassium t-butoxide in 300 ml ofdehydrated THF was cooled to 0° C., added with 5.6 g (10.0 mmol) of thewhite solid obtained above, and then, stirred at 0° C. for one hour.After adding 7.1 g (50.0 mmol) of methyl iodide gradually, the stirringwas continued at room temperature for 4 h.

After the reaction, the reaction solution was added with 100 ml of waterand extracted with dichloromethane. The organic layer was dried overMgSO₄, filtered, and concentrated. The concentrate was purified bysilica gel column chromatography, to obtain a white solid. The crudeproduct was recrystallized from toluene, to obtain 3.5 g of white solid,which was identified as the following aromatic heterocyclic derivative(H9) by FD-MS analysis (yield: 59%).

Synthesis Example 10 Production of Aromatic Heterocyclic Derivative(H10)

The reaction of Synthesis Example 9 was repeated except for using 6.5 gof intermediate 1-5 in place of intermediate 1-6 and using 5.7 g ofintermediate 2-9 in place of intermediate 2-8, to obtain 6.1 g of whitecrystal, which was identified as the following intermediate (10-a) byFD-MS analysis.

In an argon atmosphere, 10 ml (20.0 mmol) of a 2 M aqueous solution ofNa₂CO₃, 20 ml of DME, 20 ml of toluene, and 0.58 g (0.5 mmol) ofPd[PPh₃]₄ were added to a mixture of 5.5 g (10.0 mmol) of intermediate9-a and 3.4 g (12.0 mmol) of intermediate 1-8. The resultant mixture wasstirred for 12 h while refluxing under heating.

After the reaction, the reaction solution was cooled to roomtemperature, added with 50 ml of water, and then, extracted withdichloromethane in a separatory funnel. The organic layer was dried overMgSO₄, filtered, and concentrated. The obtained reaction product waspurified by silica gel column chromatography, to obtain a white solid.The crude product was recrystallized from toluene to obtain 3.3 g ofwhite solid, which was identified as the following aromatic heterocyclicderivative (H10) by FD-MS analysis (yield: 45%).

Synthesis Example 11 Production of Aromatic Heterocyclic Derivative(H11)

The reaction of Synthesis Example 1 was repeated except for using 2.5 gof intermediate 1-9 in place of intermediate 1-5, to obtain 1.5 g ofwhite crystal, which was identified as the following aromaticheterocyclic derivative (H11) by FD-MS analysis (yield: 30%).

Synthesis Example 12 Production of Aromatic Heterocyclic Derivative(H12)

The reaction of Synthesis Example 1 was repeated except for using 2.5 gof intermediate 1-9 in place of intermediate 1-5 and using 3.3 g ofintermediate 2-3 in place of intermediate 2-1, to obtain 1.7 g of whitecrystal, which was identified as the following aromatic heterocyclicderivative (H12) by FD-MS analysis (yield: 34%).

Synthesis Example 13 Production of Aromatic Heterocyclic Derivative(H13)

The reaction of Synthesis Example 10 was repeated except for using 4.9 gof intermediate 1-9 in place of intermediate 1-5, to obtain 1.9 g ofwhite crystal, which was identified as the following aromaticheterocyclic derivative (H11) by FD-MS analysis (yield: 30%).

Example 1 Production of Organic EL Device

A glass substrate with an ITO transparent electrode having a size of 25mm×75 mm×1.1 mm (manufactured by GEOMATEC Co., Ltd.) was ultrasonicallycleaned in isopropyl alcohol for 5 min and then UV (ultraviolet)/ozonecleaned for 30 min.

The cleaned glass substrate with the transparent electrode line wasmounted on the substrate holder of a vacuum deposition apparatus. First,the following electron-accepting compound (A) was vapor-deposited ontothe surface on the side where the transparent electrode line was formedso as to cover the transparent electrode, thereby forming a film Ahaving a thickness of 5 nm. On the film A, the following aromatic aminederivative (X1) as a first hole transporting material wasvapor-deposited to form a first hole transporting layer having athickness of 157 nm. Successively after the formation of the first holetransporting layer, the aromatic heterocyclic derivative (H1) obtainedin Synthesis Example 1 as a second hole transporting material wasvapor-deposited to form a second hole transporting layer having athickness of 10 nm.

On the hole transporting layer, the compound (B) (host forphosphorescence) and Ir(ppy)₃ (dopant for phosphorescence) were vaporco-deposited in to a film having a thickness of 40 nm, to form aphosphorescent light emitting layer. The concentration of Ir(ppy)₃ was10% by mass.

Then, a film of the compound (C) having a thickness of 20 nm, a film ofLiF having a thickness of 1 nm, and a film of metallic Al having athickness of 80 nm were successively deposited to form a cathode. TheLiF film as the electron injecting electrode was formed at afilm-forming speed of 1 Å/min.

Evaluation of Emission Performance of Organic EL Device

The organic EL device thus produced was measured for the luminance (L)and the current density by allowing the device to emit light under adirect current drive, thereby determining the current efficiency (L/J)and the driving voltage (V) at a current density of 10 mA/cm². Inaddition, the organic EL device was measured for the lifetime at aninitial luminance of 20000 cd/m². The results are shown in Table 1.

Examples 2 to 13

Each organic EL device was produced in the same manner as in Example 1except for using each aromatic heterocyclic derivative listed in Table 1as the second hole transporting material in place of the aromaticheterocyclic derivative (H1). Each of the obtained organic EL deviceswas measured for the luminance (L) and the current density by allowingthe device to emit light under a direct current drive, therebydetermining the current efficiency (L/J) and the driving voltage (V) ata current density of 10 mA/cm². In addition, each organic EL device wasmeasured for the lifetime at an initial luminance of 20000 cd/m². Theresults are shown in Table 1.

Comparative Examples 1 to 6

Each organic EL device was produced in the same manner as in Example 1except for using each of the following comparative compounds 1 to 6 asthe second hole transporting material in place of the aromaticheterocyclic derivative (H1). Each of the obtained organic EL deviceswas measured for the luminance (L) and the current density by allowingthe device to emit light under a direct current drive, therebydetermining the current efficiency (L/J) and the driving voltage (V) ata current density of 10 mA/cm². In addition, each organic EL device wasmeasured for the lifetime at an initial luminance of 20000 cd/m². Theresults are shown in Table 1.

TABLE 1 Results of measurements emission driving Second hole efficiencyvoltage 80% transporting (cd/A) (V) lifetime material @ 10 mA/cm² @ 10mA/cm² (h) Examples 1 H1 56.5 4.1 135 2 H2 54.2 4.1 120 3 H3 55.3 4.2125 4 H4 54.2 3.8 120 5 H5 53.7 3.8 100 6 H6 53.6 3.8 110 7 H7 58.5 4.3150 8 H8 58.7 4.3 150 9 H9 59.2 4.0 150 10  H10 59.5 4.0 150 11  H1161.2 4.2 135 12  H12 60.5 4.0 125 13  H13 61.2 4.2 150 ComparativeExamples 1 comparative 37.2 4.5 50 compound 1 2 comparative 37.0 4.3 40compound 2 3 comparative 36.6 4.3 40 compound 3 4 comparative 50.5 4.1100 compound 4 5 comparative 53.4 4.0 20 compound 5 6 comparative 50.24.1 100 compound 6

Upon comparing Example 1 with Example 2 or comparing Example 4 withExample 5, it can be found that a preferred result is obtained when L₂is boned at the 4-position of the structure represented by formula (1c).

Upon comparing Example 1 with Example 3 or comparing Example 4 withExample 6, it can be found that a preferred result is obtained when L₂is a phenylene group.

Upon comparing Examples 7 and 8 with Example 9 or Example 10, it can befound that a preferred result is obtained when X is CR₆R₇.

Upon comparing Examples 9 to 13, it can be found that L₂ is preferably aphenylene group or a single bond and particularly preferably a singlebond, and further found that X is preferably CR₆R₇.

As seen from Table 1, the nitrogen-containing aromatic heterocyclicderivative of the invention is useful as the material for realizing along-lifetime organic EL device capable of driving at high efficiency.

INDUSTRIAL APPLICABILITY

As described in detail, a highly efficient long-lifetime organic ELdevice can be obtained by using the nitrogen-containing aromaticheterocyclic derivative of the invention. Therefore, the organic ELdevice of the invention is extremely useful as light source of variouselectronic equipments, etc.

1. An aromatic heterocyclic derivative represented by formula (1-1) or(1-2):

wherein: ring A is represented by formula (1a) or (1b):

ring carbon atoms C₁ and C₂, C₃ and C₄, C₄ and C₅, or C₅ and C₆ areshared with an adjacent ring; X represents NR₅, CR₆R₇, SiR₆R₇, an oxygenatom, or a sulfur atom; each of W and Z independently represents asingle bond, CR₆R₇, SiR₆R₇, an oxygen atom, or a sulfur atom; L₁represents a single bond, an arylene group comprising from 6 to 30 ringcarbon atoms, or a heteroarylene group comprising from 5 to 30 ringatoms; each of R₁ to R₇ independently represents a linear or branchedalkyl group comprising from 1 to 15 carbon atoms, a cycloalkyl groupcomprising from 3 to 15 ring carbon atoms, a substituted or anunsubstituted silyl group, an aryl group comprising from 6 to 30 ringcarbon atoms, a heteroaryl group comprising from 5 to 30 ring atoms, ahalogen atom, or a cyano group, or adjacent two groups of R₁ to R₇ arebonded to each other to from a saturated or an unsaturated divalentgroup which completes a ring; each of a, c and d independentlyrepresents an integer of 0 to 4; b represents an integer of 0 to 3; erepresents an integer of 0 to 2; and Q represents a structurerepresented by formula (1c):

wherein: Y represents an oxygen atom or a sulfur atom; L₂ represents asingle bond, an arylene group comprising from 6 to 30 ring carbon atoms,or a heteroarylene group comprising from 5 to 30 ring atoms, providedthat when L₂ is bonded to a carbon atom at 2-position of the structurerepresented by formula (1c), L₂ represents an arylene group comprisingfrom 6 to 30 ring carbon atoms or a heteroaryl group comprising from 5to 30 ring atoms; each of R₈ and R₉ independently represents a linear orbranched alkyl group comprising from 1 to 15 carbon atoms, a cycloalkylgroup comprising from 3 to 15 ring carbon atoms, a substituted or anunsubstituted silyl group, an aryl group comprising from 6 to 30 ringcarbon atoms, a heteroaryl group comprising from 5 to 30 ring atoms, ahalogen atom, or a cyano group, or adjacent two groups of R₈ and R₉ arebonded to each other to from a saturated or an unsaturated divalentgroup which completes a ring; f represents an integer of 0 to 3; and grepresents an integer of 0 to
 4. 2. The aromatic heterocyclic derivativeaccording to claim 1, wherein W of formulae (1-1) and (1-2) represents asingle bond, and Z of formulae (1a) and (1b) represents a single bond.3. The aromatic heterocyclic derivative according to claim 2, which isrepresented by formula (2-1) or (2-2):

.
 4. The aromatic heterocyclic derivative according to claim 2, which isrepresented by formula (3-1) or (3-2):

.
 5. The aromatic heterocyclic derivative according to claim 2, which isrepresented by formula (4-1):

.
 6. The aromatic heterocyclic derivative according to claim 2, which isrepresented by formula (5-1) or (5-2):

.
 7. The aromatic heterocyclic derivative according to claim 1, whereinL₂ represents a single bond.
 8. The aromatic heterocyclic derivativeaccording to claim 1, wherein L₂ represents a structure represented byany one of formulae (7a) to (7c):

each of R₁₁ to R₁₃ independently represents a linear or branched alkylgroup comprising from 1 to 15 carbon atoms, a cycloalkyl groupcomprising from 3 to 15 ring carbon atoms, a substituted or anunsubstituted silyl group, an aryl group comprising from 6 to 20 ringcarbon atoms, a heteroaryl group comprising from 5 to 20 ring atoms, ahalogen atom, or a cyano group, or adjacent two groups of R₁₁ to R₁₃ arebonded to each other to from a saturated or an unsaturated divalentgroup which completes a ring; each of R₁₄ and R₁₅ independentlyrepresents a linear or branched alkyl group comprising from 1 to 15carbon atoms, a cycloalkyl group comprising from 3 to 15 ring carbonatoms, an aryl group comprising from 6 to 20 ring carbon atoms, or aheteroaryl group comprising from 5 to 20 ring atoms; and each of k1 tok3 independently represents an integer of 0 to
 4. 9. The aromaticheterocyclic derivative according to claim 1, wherein X represents NR₅.10. The aromatic heterocyclic derivative according to claim 1, wherein Xrepresents an oxygen atom.
 11. The aromatic heterocyclic derivativeaccording to claim 1, wherein X represents a sulfur atom.
 12. Thearomatic heterocyclic derivative according to claim 1, wherein Xrepresents CR₆R₇.
 13. The aromatic heterocyclic derivative according toclaim 1, wherein X represents SiR₆R₇.
 14. The aromatic heterocyclicderivative according to claim 1, wherein Y represents an oxygen atom.15. The aromatic heterocyclic derivative according to claim 1, wherein Yrepresents a sulfur atom.
 16. The aromatic heterocyclic derivativeaccording to claim 1, wherein L₂ is bonded to a carbon atom at4-position of the structure represented by formula (1c).
 17. A materialfor organic electroluminescence device, comprising the aromaticheterocyclic derivative according to claim
 1. 18. A hole transportingmaterial for organic electroluminescence device, comprising the aromaticheterocyclic derivative according to claim
 1. 19. An organicelectroluminescence device, comprising: a light emitting layer, andorganic thin film layers between an anode and a cathode, wherein atleast one of the organic thin film layers comprises the aromaticheterocyclic derivative according to claim
 1. 20. The organicelectroluminescence device according to claim 19, wherein the organicthin film layers comprise a hole transporting layer, and the holetransporting layer comprises the aromatic heterocyclic derivative. 21.The organic electroluminescence device according to claim 19, whereinthe light emitting layer comprises a phosphorescent material.
 22. Theorganic electroluminescence device according to claim 21, wherein thephosphorescent material is an ortho metallated complex of a metalselected from the group consisting of iridium (Ir), osmium (Os) andplatinum (Pt).
 23. The organic electroluminescence device according toclaim 20, wherein the hole transporting layer contacts a layercomprising a compound represented by formula (A):

R²¹ to R²⁶ each independently represent a cyano group, —CONH₂, acarboxyl group, or —COOR²⁷, R²⁷ represents an alkyl group comprisingfrom 1 to 20 carbon atoms or a cycloalkyl group comprising from 3 to 20carbon atoms; and one or more of a pair of R²¹ and R²², a pair of R²³and R²⁴, and a pair of R²⁵ and R²⁶ optionally bond to each other to forma group represented by —CO—O—CO—.